JP5104756B2 - Plasma display device - Google Patents

Description

  The present invention relates to a plasma display device used for a wall-mounted television or a large monitor.

  A plasma display panel (hereinafter abbreviated as “panel”), which is a typical image display device having a large number of pixels arranged in a plane, has a large number of discharges as pixels between a front plate and a back plate arranged opposite to each other. A cell is formed. In the front plate, a plurality of display electrode pairs each consisting of a pair of scan electrodes and sustain electrodes are formed in parallel with each other on the front glass substrate, and a dielectric layer and a protective layer are formed so as to cover the display electrode pairs. Yes. The back plate has a plurality of parallel data electrodes on the back glass substrate, a dielectric layer so as to cover them, and a plurality of barrier ribs in parallel with the data electrodes formed on the back glass substrate. A phosphor layer is formed on the side walls of the barrier ribs. Then, the front plate and the rear plate are arranged opposite to each other so that the display electrode pair and the data electrode are three-dimensionally crossed and sealed, and a discharge gas is sealed in the internal discharge space. Here, a discharge cell is formed at a portion where the display electrode pair and the data electrode face each other. In the panel having such a configuration, ultraviolet light is generated by gas discharge in each discharge cell, and phosphors of RGB colors are excited and emitted by the ultraviolet light to perform color display.

  The subfield method is used as a method for driving the panel. In this method, one field period is divided into a plurality of subfields (hereinafter, the subfield is also abbreviated as “SF”), and each discharge cell emits light or does not emit light in each subfield. It is. Each subfield has an initialization period, an address period, and a sustain period. In the initializing period, initializing discharge is performed in the discharge cells, and wall charges necessary for the subsequent address operation are formed. In the address period, a scan pulse voltage is sequentially applied to the scan electrodes, and an address pulse voltage corresponding to an image signal to be displayed is applied to the data electrodes, and an address discharge is selectively performed between the scan electrodes and the data electrodes. Wake up and perform selective wall charge formation. In the subsequent sustain period, a predetermined number of sustain pulse voltages corresponding to the display luminance to be emitted are applied between the scan electrode and the sustain electrode, and the discharge cells in which the wall charges are formed by the address discharge are selectively discharged. Make it emit light. The ratio of display luminance for each subfield is referred to as “luminance weight”.

  The plasma display device includes a scan electrode drive circuit for driving the scan electrode, a sustain electrode drive circuit for driving the sustain electrode, and a data electrode drive circuit for driving the data electrode to drive the panel, The drive circuit of each electrode applies a necessary drive voltage waveform to each electrode. Here, when viewed from the data electrode drive circuit side, each data electrode is a capacitive load having a combined capacity of the adjacent data electrode, scan electrode, and sustain electrode. Therefore, in order to apply a drive voltage waveform to each data electrode, this capacity must be charged and discharged. The power consumption of the data electrode drive circuit is not only the discharge associated with the address discharge, but rather the ratio of the power consumption associated with the charge / discharge of the capacity of the data electrode is large. The charge / discharge current largely depends on the image signal to be displayed. For example, when the address pulse voltage is not applied to all the data electrodes, the charge / discharge current is 0, so that the power consumption is minimized. Similarly, when the address pulse voltage is applied to all the data electrodes, the charge / discharge current is 0, so the power consumption is small. However, when the address pulse voltage is randomly applied to the data electrodes, the charge / discharge current increases, and the power consumption of the data electrode drive circuit also increases.

  Thus, the power consumption of the data electrode driving circuit varies greatly depending on the image signal. Therefore, the power supply for the data electrode that supplies power to the data electrode drive circuit has a sufficiently large power supply capability so that normal write operation can be performed even when the power consumption of the data electrode drive circuit is maximized. Has been designed to be. However, as the screen size and resolution of the panel increase, the maximum power consumption has become much larger than the power consumption during normal image display. Even in such a case, it is not economical to design the power supply for the data electrode so that the necessary power can be supplied.

  Therefore, the power consumption of the data electrode driving circuit is predicted based on the image signal to be displayed, and when the predicted value exceeds the set value, the writing operation of the subfield with a small luminance weight is stopped and the gradation is limited. Discloses a technique for reducing power consumption (see, for example, Patent Document 1). Also disclosed is a method of actually detecting the power consumption of the data electrode drive circuit and limiting the gradation when the power consumption increases (see, for example, Patent Document 2). Further, a method is disclosed in which the temperature of the data electrode driving circuit is estimated based on the image data in which the image signal is associated with the subfield, and when the estimated temperature is high, the image signal is converted to lower the temperature of the data electrode driving circuit. (For example, refer to Patent Document 3).

However, for example, in the method of limiting the gradation based on the power consumption in the data electrode driving circuit as in Patent Document 1 and Patent Document 2, the increase and decrease in power consumption are repeated at an early cycle. The possibility of the phenomenon increases. For example, in a configuration in which a protection circuit is added to the data electrode driving circuit, the protection circuit frequently performs a protection operation. Therefore, there is a possibility that a stable display operation cannot be performed, such as temporarily stopping image display for protection. On the other hand, for example, the method of limiting gradation based on the temperature in the data electrode driving circuit as in Patent Document 3 can suppress the phenomenon that the protective circuit frequently performs protective operation, but the power consumption rapidly increases. There was a problem that it was not possible to respond immediately. In addition, when the power consumption and temperature increase and decrease are repeated, gradation limitation and non-limitation are repeated. The repetition of the gradation limitation causes flicker on the display image, which causes a problem that the image quality is deteriorated.
JP 2000-66638 A JP 2003-271094 A JP 2002-149109 A

The plasma display apparatus of the present invention uses a plasma display panel in which discharge cells are formed at the intersections between display electrode pairs and data electrodes, and divides one field period of an image signal into a plurality of subfields. An image display device that displays an image by causing each discharge cell to emit or not emit light, and that converts an image signal into image data for causing each discharge cell to emit or not emit light in each subfield period. A signal conversion circuit; a data electrode drive circuit that drives the data electrode based on the image data; a power calculation unit that calculates power consumption of the data electrode drive circuit based on the image data and outputs the calculated power value; and calculating a temperature of the data electrode driving circuit and the temperature calculated value based And a temperature calculation unit for outputting. Then, the image signal conversion circuit determines the number of subfields to be converted into image data for reducing the power consumption of the data electrode driving circuit in accordance with each of the power calculation value and the temperature calculation value, and sets the number of target SFs. The image signal is converted into image data based on the larger one of the number of target SFs determined according to the value and the number of target SFs determined according to the temperature calculation value .

  With this configuration, even if an image signal that increases the power consumption of the data electrode drive circuit is input, it is possible to respond immediately to a rapid increase in power consumption, and the data electrode drive circuit malfunctions. And image display can be performed with stable operation.

In the plasma display device of the present invention, the image signal conversion circuit has a first temperature threshold value and a second temperature threshold value smaller than the first temperature threshold value. Then, the image signal conversion circuit, when at least the power calculated value exceeds a predetermined power threshold, or if the temperature calculated value exceeds the first temperature threshold value, the image signal, reducing the power consumption of the data electrode driving circuit Convert to image data. The image signal conversion circuit converts the image signal into the power consumption of the data electrode driving circuit when at least the calculated power value is equal to or lower than a predetermined power threshold value or when the calculated temperature value is equal to or lower than the second temperature threshold value. The image data may be converted into image data that increases the image quality.

In the plasma display device of the present invention, the image signal conversion circuit has a first power threshold value and a second power threshold value smaller than the first power threshold value. Then, the image signal conversion circuit, when at least the power calculated value exceeds the first power threshold, or if the temperature calculated value exceeds a predetermined temperature threshold value, the image signal, reducing the power consumption of the data electrode driving circuit Convert to image data. The image signal conversion circuit converts the image signal into the power consumption of the data electrode driving circuit when at least the power calculation value is equal to or lower than the second power threshold value or when the temperature calculation value is equal to or lower than the predetermined temperature threshold value. The image data may be converted into image data that increases the image quality.

  With this configuration, even if an image signal that increases the power consumption of the data electrode driving circuit is input, it is possible to respond immediately to a rapid increase in power consumption, and the data electrode driving circuit malfunctions. In addition, image display can be performed with stable operation while suppressing flicker and the like.

  In the plasma display device of the present invention, the data electrode driving circuit has a plurality of driving units respectively corresponding to the data electrodes of the plasma display panel divided for each block. The power calculation unit may calculate the total power consumption of the plurality of drive units, and the temperature calculation unit may calculate the highest temperature among the plurality of drive units.

  With this configuration, it is possible to immediately cope with a rapid increase in power consumption by comparing the calculated total power consumption of the drive unit with a predetermined power threshold. Also, by comparing the highest temperature of each drive unit with a predetermined temperature threshold, the temperature rise of each drive unit can be suppressed based on the drive unit with the highest temperature rise, and all drive units have problems due to temperature rise. Can be protected from.

  In the plasma display device of the present invention, the image signal conversion circuit may reduce power consumption of the data electrode driving circuit in at least one subfield.

  With this configuration, it is possible to reduce the power consumption of the data electrode driving circuit only by stopping the write operation in the corresponding subfield without changing the coding table.

  Hereinafter, a plasma display device according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is an exploded perspective view showing a main part of a panel 10 according to an embodiment of the present invention. The panel 10 is configured such that a glass front substrate 21 and a rear substrate 31 are arranged to face each other and a discharge space is formed therebetween. On the front substrate 21, a plurality of scanning electrodes 22 and sustaining electrodes 23 constituting the display electrode pair 24 are formed in parallel with each other. A dielectric layer 25 is formed so as to cover the scan electrode 22 and the sustain electrode 23, and a protective layer 26 is formed on the dielectric layer 25. A plurality of data electrodes 32 are formed on the back substrate 31, and a dielectric layer 33 is formed so as to cover the data electrodes 32. On the dielectric layer 33, a grid-like partition wall 34 is provided. Further, a phosphor layer 35 is provided on the surface of the dielectric layer 33 and the side surfaces of the partition walls 34. The front substrate 21 and the rear substrate 31 are arranged to face each other in the direction in which the scan electrode 22 and the sustain electrode 23 intersect with the data electrode 32, and in the discharge space formed therebetween, for example, neon And a mixed gas of xenon. Note that the structure of the panel 10 is not limited to the above-described structure, and for example, the panel 10 may include a stripe-shaped partition wall.

  FIG. 2 is an electrode array diagram of panel 10 in accordance with the exemplary embodiment of the present invention. N scanning electrodes SC1 to SCn (scanning electrode 22 in FIG. 1) and n sustaining electrodes SU1 to SUn (sustaining electrode 23 in FIG. 1), which are long in the row direction, are arranged and m long in the column direction. The data electrodes D1 to Dm (data electrodes 32 in FIG. 1) are arranged. A discharge cell is formed at a portion where a pair of scan electrode SCi and sustain electrode SUi (i = 1 to n) and one data electrode Dj (j = 1 to m) intersect, and the discharge cell is in the discharge space. M × n are formed.

  Next, a driving voltage waveform for driving the panel 10 will be described. In the present embodiment, one field is divided into 10 subfields (“first SF”, “second SF”,..., “10th SF”), and each subfield is, for example, “1”, “ An explanation will be given by giving an example having luminance weights of “2”, “3”, “6”, “11”, “18”, “30”, “44”, “60”, “80”. As described above, in the present embodiment, the luminance weight is set to be larger as the luminance weight of the subfield arranged later. However, in the present invention, the number of subfields and the luminance weight of each subfield are not limited to the above values.

  FIG. 3 is a diagram showing drive voltage waveforms applied to the respective electrodes of panel 10 in accordance with the exemplary embodiment of the present invention.

  In the initialization period, first, in the first half, data electrode D1 to data electrode Dm and sustain electrode SU1 to sustain electrode SUn are held at 0 V, and voltage Vi1 that is equal to or lower than the discharge start voltage with respect to scan electrode SC1 to scan electrode SCn. A ramp voltage that gradually rises toward a voltage Vi2 exceeding the discharge start voltage is applied. Then, weak initializing discharge is caused in all the discharge cells, and wall voltage is accumulated on scan electrode SC1 through scan electrode SCn, sustain electrode SU1 through sustain electrode SUn, and data electrode D1 through data electrode Dm. Here, the wall voltage on the electrode refers to a voltage generated by wall charges accumulated on a dielectric layer covering the electrode, a phosphor layer, or the like.

  Subsequently, in the latter half of the initialization period, sustain electrode SU1 through sustain electrode SUn are maintained at voltage Ve1, and a ramp voltage that gradually decreases from voltage Vi3 to voltage Vi4 is applied to scan electrode SC1 through scan electrode SCn. Then, weak initializing discharge is caused again in all the discharge cells, and the wall voltages on scan electrode SC1 through scan electrode SCn, sustain electrode SU1 through sustain electrode SUn, and data electrode D1 through data electrode Dm are values suitable for the write operation. Adjusted to

  In some of the subfields constituting one field, the first half of the initializing period may be omitted. In this case, the discharge cells that have been subjected to the sustain discharge in the immediately preceding subfield may be omitted. An initialization operation is selectively performed. FIG. 3 shows drive voltage waveforms for performing the initialization operation having the first half and the second half in the initialization period of the first SF, and performing the initialization operation having only the second half in the initialization period of the subfield after the second SF. .

  In the address period, voltage Ve2 is applied to sustain electrode SU1 through sustain electrode SUn. The address pulse voltage Vd is applied to the data electrode Dk (k = 1 to m) of the discharge cell that should emit light in the first row among the data electrodes D1 to Dm, and the scan pulse is applied to the scan electrode SC1 in the first row. A voltage Va is applied. Then, an address discharge occurs between data electrode Dk and scan electrode SC1 and between sustain electrode SU1 and scan electrode SC1, and a positive wall voltage is generated on scan electrode SC1 and a negative voltage is applied on sustain electrode SU1. Wall voltage is accumulated. In this way, the address operation is performed in which the address discharge is caused in the discharge cells to emit light in the first row and the wall voltage is accumulated on each electrode. On the other hand, no address discharge occurs at the intersection between the data electrode Dh (h ≠ k) to which the address pulse voltage Vd is not applied and the scan electrode SC1. The above address operation is sequentially performed until the discharge cell in the nth row, and the address period ends.

  As described above, each of the data electrodes D1 to Dm is driven by a data electrode driving circuit which will be described later, but when viewed from the data electrode driving circuit, each data electrode Dj is a capacitive load. Therefore, in the address period, this capacitance must be charged and discharged each time the voltage applied to each data electrode is changed from the ground potential 0 V to the address pulse voltage Vd or from the address pulse voltage Vd to the ground potential 0 V. If the number of times of charging / discharging is large, the power consumption of the data electrode driving circuit also increases.

  In the subsequent sustain period, sustain electrode SU1 through sustain electrode SUn is returned to 0 V, and sustain pulse voltage Vs is applied to scan electrode SC1 through scan electrode SCn. In the discharge cell that has caused the address discharge at this time, the voltage between scan electrode SCi and sustain electrode SUi is the sustain pulse voltage Vs plus the wall voltage on scan electrode SCi and sustain electrode SUi. Exceeds the discharge start voltage. A sustain discharge occurs between scan electrode SCi and sustain electrode SUi, and light is emitted. At this time, a negative wall voltage is accumulated on scan electrode SCi, and a positive wall voltage is accumulated on sustain electrode SUi. Subsequently, scan electrode SC1 to scan electrode SCn are returned to 0 V, and sustain pulse voltage Vs is applied to sustain electrode SU1 to sustain electrode SUn. Then, in the discharge cell in which the sustain discharge has occurred, the voltage between sustain electrode SUi and scan electrode SCi exceeds the discharge start voltage, so that a sustain discharge occurs again between sustain electrode SUi and scan electrode SCi. As a result, a negative wall voltage is accumulated on sustain electrode SUi, and a positive wall voltage is accumulated on scan electrode SCi.

  Thereafter, similarly, by applying the number of sustain pulse voltages proportional to the luminance weight to scan electrode SC1 through scan electrode SCn and sustain electrode SU1 through sustain electrode SUn, the sustain operation is performed in the discharge cells that have caused the address discharge in the address period. Discharging continues. Note that the sustain discharge does not occur in the discharge cells that did not cause the address discharge in the address period, and the wall voltage at the end of the initialization period is maintained. Thus, the maintenance operation in the maintenance period is completed.

  Also in the subsequent second to tenth SFs, the initialization period and the writing period are the same as those of the first SF, and the sustain period is the same as the sustain period of the first SF except for the number of sustain pulses. In this way, each discharge cell is controlled to emit light or not emit light for each subfield, and image display is performed by combining the luminance weights of the subfields.

  FIG. 4 is a circuit block diagram of the plasma display device in accordance with the first exemplary embodiment of the present invention. The plasma display device according to the present embodiment includes a panel 10, an image signal conversion circuit 40, a data electrode drive circuit 52, a scan electrode drive circuit 53, a sustain electrode drive circuit 54, a timing generation circuit 55, a data electrode load calculation circuit 60, a temperature. A temperature calculation circuit 61 as a calculation unit, a power calculation circuit 62 as a power calculation unit, and a power supply circuit (not shown) that supplies necessary power to each circuit block are provided.

  The timing generation circuit 55 generates various timing signals for controlling the operation of each circuit block based on the horizontal synchronization signal and the vertical synchronization signal, and supplies them to the respective circuit blocks. Scan electrode drive circuit 53 applies the drive voltage waveforms shown in FIG. 3 to scan electrode SC1 through scan electrode SCn, respectively, based on various timing signals. In addition, sustain electrode drive circuit 54 applies the drive voltage waveform shown in FIG. 3 to sustain electrode SU1 through sustain electrode SUn based on various timing signals.

  The image signal conversion circuit 40 converts the input image signal into image data indicating light emission / non-light emission for each subfield. For simplicity of explanation, it is assumed that the image signal is a primary color signal of red, green, and blue, and each of the primary color signals is a digital signal having a minimum value of “0” and a maximum value of “255”.

  5A, 5B, and 5C are diagrams showing examples of the relationship between the image signal and the image data in the embodiment of the present invention. In this way, the relationship indicating in which subfield the discharge cell emits light with respect to the input image signal is hereinafter abbreviated as “coding”. In FIGS. 5A, 5B, and 5C, the numerical values shown in the leftmost column indicate values corresponding to the luminance of the image signal, and on the right side, the discharge cell is displayed in each subfield when displaying the luminance of the corresponding image signal. Whether or not to emit light is indicated, “0” indicates non-light emission, and “1” indicates light emission. As shown in FIG. 5A, for example, when the primary color signal “1” is input, the discharge cell is caused to emit light only in the first subfield having the luminance weight 1, and the luminance “1” is displayed. When the primary color signal “7” is input, the discharge cell is caused to emit light by the first SF having the luminance weight “1” and the fourth SF having the luminance weight “6”, and the luminance “7” is displayed. When the primary color signal “14” is input, the discharge cell is caused to emit light by the first SF having the luminance weights “1” and “2”, the second SF, and the fifth SF having the luminance weight “11”, and the luminance “ 14 "is displayed. In addition, when displaying the luminance “3”, there are a method of causing the discharge cells to emit light with the first SF and the second SF, and a method of causing only the third SF to emit light, but when multiple coding is possible in this way Is selected to be lit in a subfield having as small a luminance weight as possible. That is, when the luminance “3” is displayed, the discharge cells are caused to emit light by the first SF and the second SF as shown in FIG. 5A. The circuit for converting the image signal as described above into image data can be realized by using a data conversion table using a ROM or the like.

  The image signal conversion circuit 40 changes the coding based on conversion control data described later. The conversion control data is data indicating that at least the power consumption of the data electrode driving circuit 52 is larger than a predetermined power threshold and the temperature is larger than a predetermined temperature threshold. Based on the conversion control data, the image signal conversion is performed. The circuit 40 converts the image data into image data that reduces the power consumption of the data electrode driving circuit 52. Specifically, in the present embodiment, roughly, when the image signal conversion circuit 40 determines that at least one of the power consumption and the temperature of the data electrode driving circuit 52 has increased, for example, in the subfield having a small luminance weight, Change to coding that does not perform write operations.

  5B and 5C are diagrams showing another example of coding changed based on the conversion control data in the present embodiment, FIG. 5B is coding in which no write operation is performed in the first SF, and FIG. 5C is the first SF and the first SF. The coding in which the writing operation is not performed in 2SF is shown. Although not shown, the same applies to coding in which no writing operation is performed in the first SF to third SF, coding in which writing operation is not performed in the first SF to fourth SF, and the like. For example, as shown in FIG. 5B, according to the coding in which the writing operation is not performed in the first SF, the luminance “1”, “3”, “4”, “6”,. However, since no write operation is performed in the first SF, power consumption can be reduced accordingly. In this way, when the number of subfields not performing the write operation is increased, the number of luminances that can be displayed is reduced, but the power consumption for the write operation can be reduced.

  The coding change as described above may be realized by switching between a plurality of data conversion tables. For example, the bit corresponding to the image data indicating light emission / non-light emission for each subfield is set to “0”. It can also be easily realized by fixing to "." Further, as described above, the power consumption of the data electrode driving circuit is reduced in the case where the address pulse voltage is applied to all the data electrodes in addition to the case where the address pulse voltage is not applied to all the data electrodes.

  For this reason, instead of the coding that does not perform the write operation in the subfield as shown in FIG. 5B or FIG. In this case, the coding may be changed so that the writing operation is performed in the subfield having a small luminance weight. In this case, for example, it can be easily realized by fixing the corresponding bit of the image data indicating light emission / non-light emission for each subfield to “1”. Hereinafter, in the embodiment of the present invention, an example using coding in which a write operation is not performed in a subfield as shown in FIGS. 5B and 5C will be described.

  The image signal conversion circuit 40 converts the image signal into image data for causing the discharge cells to emit light or not in each subfield period. In particular, in this conversion processing, the image signal conversion circuit 40 converts the image signal into the data electrode when at least the power consumption of the data electrode driving circuit 52 is larger than a predetermined power threshold and when the temperature is larger than a predetermined temperature threshold. The image data is converted into image data that reduces the power consumption of the drive circuit 52. Details of this conversion processing will be described below.

  The image signal conversion circuit 40 supplies the image data generated as described above to the data electrode driving circuit 52. The data electrode drive circuit 52 converts the image data for each subfield into signals corresponding to the data electrodes D1 to Dm, and drives the data electrodes D1 to Dm, respectively.

  The image data generated by the image signal conversion circuit 40 is also supplied to the data electrode load calculation circuit 60. The data electrode load calculation circuit 60 calculates the load amount in each field of the data electrode drive circuit 52 by calculation.

  As described above, since the data electrode 32 is a capacitive load when viewed from the data electrode drive circuit 52, the load applied to charge and discharge the capacitance of the data electrode 32 when the voltage applied to the data electrode 32 changes frequently. Becomes heavier. As a result, the power consumption of the data electrode driving circuit 52 increases. For example, if an address pulse voltage is applied to a discharge cell having an even-numbered scan electrode SCp (p = even) and no address pulse voltage is applied to a discharge cell having an odd-numbered scan electrode SC (p + 1) Since the voltage 0 and the voltage Vd are alternately applied to the data electrode Dj, the power consumption increases. In addition, when the adjacent data electrodes D (j−1) and D (j + 1) are alternately applied with the voltage 0 and the voltage Vd in opposite phases, the power consumption is further increased.

  Conversely, when no write pulse voltage is applied to all data electrodes 32, the power consumption is minimized, and when the write pulse voltage is applied to all data electrodes 32, the power consumption is small. During normal image display, the power consumption of the data electrode driving circuit 52 varies according to the image signal. In addition, for this reason, in the case of a checkered pattern image signal in which the light emission state of each adjacent discharge cell is reversed with respect to the target discharge cell, the number of changes in the address pulse voltage increases. The power consumption of 52 also increases.

  Based on the relationship between the driving state of each discharge cell and the power consumption, the data electrode load calculation circuit 60 calculates, for example, an exclusive OR of data between the left and right and upper and lower discharge cells in each subfield of the image data. Thus, a change in the write pulse voltage may be detected. Furthermore, the data electrode load calculation circuit 60 detects the number of changes in the write pulse voltage by obtaining the sum of these calculation results, and the load of the data electrode drive circuit 52 estimated in units of fields based on the number of changes. The amount may be calculated. The data electrode load calculation circuit 60 notifies the temperature calculation circuit 61 and the power calculation circuit 62 of the load amount thus calculated as a load value.

  The temperature calculation circuit 61 calculates the temperature in the data electrode drive circuit 52 by further performing arithmetic processing on the load value calculated by the data electrode load calculation circuit 60. In addition, the power calculation circuit 62 calculates the power consumption in the data electrode drive circuit 52 by further performing arithmetic processing on the load value calculated by the data electrode load calculation circuit 60. In this way, the temperature calculation circuit 61 calculates the temperature in the data electrode drive circuit 52 based on the image data output from the image signal conversion circuit 40. The power calculation circuit 62 calculates the power consumption in the data electrode driving circuit 52 based on the image data output from the image signal conversion circuit 40.

  The temperature calculation circuit 61 notifies the calculated temperature to the image signal conversion circuit 40 as a temperature calculation value TE. In addition, the power calculation circuit 62 notifies the image signal conversion circuit 40 of the calculated power consumption as a power calculation value PE.

  The image signal conversion circuit 40 generates conversion control data for conversion control of the image signal based on the notified temperature calculation value TE and power calculation value PE, and outputs the image data generated by coding based on the conversion control data. To do.

  With the configuration described above, in the plasma display device according to the present embodiment, the power calculation circuit 62 calculates the power consumption of the data electrode driving circuit 52 based on the image data output from the image signal conversion circuit 40, and the temperature The calculation circuit 61 calculates the temperature of the data electrode drive circuit 52. Further, the image signal conversion circuit 40 generates conversion control data based on the calculated power consumption and temperature. Then, based on the conversion control data, the image signal conversion circuit 40 at least when the power consumption calculated by the data electrode driving circuit 52 exceeds a predetermined power threshold, or the temperature calculated by the data electrode driving circuit 52 is a predetermined temperature. When the threshold value is exceeded, the coding is changed to a coding that does not perform a writing operation in a subfield having a small luminance weight. That is, the image signal conversion circuit 40 operates to convert the image signal into image data that reduces the power consumption of the data electrode driving circuit 52. The plasma display apparatus according to the present embodiment executes such feedback processing and adaptively controls power consumption according to the image signal.

  Next, a more detailed configuration for adaptively controlling power consumption in the plasma display device of the present embodiment will be described. FIG. 6 is a circuit block diagram showing a detailed configuration example of the main part of the circuit configuration for controlling the power consumption of the plasma display device in the first exemplary embodiment of the present invention. Here, the data electrode driving circuit 52 is constituted by an IC as a driving unit which is a plurality of driving integrated circuits. The data electrode driving circuit 52 will be described with an example in which the data electrode driving circuit 52 has a plurality of driving units respectively corresponding to the data electrodes 32 of the panel 10 divided into blocks. FIG. 6 shows an example in which there are four such drive ICs 521 included in the data electrode drive circuit 52 and the power consumption and temperature are calculated for each drive IC 521.

  First, as illustrated in FIG. 6, the image signal conversion circuit 40 includes a first image conversion unit 41, a second image conversion unit 42, and a conversion control data generation unit 43. The first image conversion unit 41 converts the supplied image signal into image data indicating light emission / non-light emission for each subfield according to a predetermined coding as shown in FIG. 5A. In addition, the second image conversion unit 42 converts the image data according to the predetermined coding, for example, brightness as illustrated in FIGS. 5B and 5C according to the conversion control data notified from the conversion control data generation unit 43. It changes to the image data of the coding which does not perform the writing operation in the subfield with a small weight. The second image conversion unit 42 supplies the image data generated in this way to each of the plurality of driving ICs 521 connected to the data electrodes 32 of the panel 10 divided for each block. Details of the conversion control data generation unit 43 will be described below.

  Next, the data electrode load calculation circuit 60 includes a plurality of load calculation circuits 601 that calculate a load value corresponding to the load amount in each field for each drive IC 521. The load calculation circuit 601 detects the number of changes in the address pulse voltage between the left and right and upper and lower discharge cells in the corresponding block of image data by the exclusive OR operation and the sum operation as described above, and the load value for each drive IC 521 Output as.

  Next, the temperature calculation circuit 61 uses a load value notified from the load calculation circuit 601 to calculate a temperature for each drive IC 521 by calculation, and a plurality of cumulative calculators 611 and output values from the cumulative calculators 611. A maximum value detector 612 for detecting and outputting the maximum value is included. Each cumulative calculator 611 calculates a predicted temperature value in the corresponding drive IC 521 by cumulatively calculating the load value corresponding to each drive IC 521. That is, in this embodiment, it is assumed that the load value calculated by the load calculation circuit 601 is proportional to the power consumption of the drive IC 521, and the load value corresponding to such power consumption is calculated by the cumulative calculator 611 for each unit time. The temperature is determined by integration. More specifically, the accumulator 611 can be realized by, for example, a recursive filter that takes heat radiation into account. That is, the heat radiation is set as a coefficient α satisfying 0 <α <1, and the load value supplied for each field is added to the load value of the current field and the output value of the previous field multiplied by α. Thus, the temperature in the drive IC 521 can be predicted. Each accumulator 611 notifies the maximum value detector 612 of the temperature determination value thus determined. The maximum value detector 612 detects the maximum value among the temperature discrimination values notified from the respective cumulative calculators 611, and notifies the detected maximum value to the image signal conversion circuit 40 as the temperature calculation value TE. Note that, as in the temperature calculation circuit 61, the temperature for each drive IC 521 may be determined and the maximum value may be obtained. That is, the highest temperature among the plurality of drive units may be calculated. With such a configuration, the temperature rise of each drive IC 521 can be suppressed based on the drive IC 521 having the highest temperature rise. Therefore, the plasma display device can reliably protect all of the drive ICs 521 from problems due to temperature rise even when there are a plurality of drive ICs 521.

  Further, the power calculation circuit 62 includes an adder 621 that calculates the sum of the load values notified from the load calculation circuit 601. In other words, in the present embodiment, it is assumed that the load value calculated by the load calculation circuit 601 is proportional to the power consumption of the drive IC 521, and the adder 621 performs the total calculation of each load value. Thereby, the power calculation circuit 62 calculates the power consumption by all the drive ICs 521, that is, the total power consumption of the plurality of drive units. The power calculation circuit 62 notifies the image signal conversion circuit 40 of the total sum of the load values thus obtained as the power calculation value PE.

  The temperature calculation value TE from the temperature calculation circuit 61 and the power calculation value PE from the power calculation circuit 62 are notified to the conversion control data generation unit 43 of the image signal conversion circuit 40. The conversion control data generation unit 43 includes a target SF number determination circuit 44 that determines the number of subfields according to the temperature calculation value TE, and a target SF number determination circuit 45 that determines the number of subfields according to the power calculation value PE. And a maximum value detector 433 that detects and outputs the maximum value among the output values of the target SF number determination circuit 44 and the target SF number determination circuit 45. Note that the number of subfields determined by the target SF number determination circuit 44 and the target SF number determination circuit 45 corresponds to the number of subfields in which no write operation is performed. The conversion control data generation unit 43 stores a temperature threshold Tth indicating a predetermined temperature value and a power threshold Pth indicating a predetermined power value. The target SF number determination circuit 44 includes the temperature threshold Tth. And the target SF number determination circuit 45 is notified of the power threshold value Pth.

  The target SF number determination circuit 44 of the conversion control data generation unit 43 determines the number of target subfields according to the calculated temperature value TE based on the notified temperature threshold value Tth, and the target corresponding to the calculated temperature value TE. Output as SF number Nte. Specifically, the target SF number determination circuit 44 is notified of one or more temperature threshold values Tth for the temperature calculation value TE. Then, the target SF number determination circuit 44 compares the temperature calculation value TE notified for each field with the temperature threshold Tth, and determines whether or not the temperature calculation value TE has exceeded a temperature threshold Tth indicating a predetermined temperature. The target SF number determination circuit 44 determines the number of target subfields based on the determination result. For example, when the first temperature threshold value and the second temperature threshold value are provided, and the calculated temperature value TE is equal to or less than the first temperature threshold value, the target SF number Nte is set to “0”, and the calculated temperature value TE is the first temperature. The target SF number Nte is set to “1” when the threshold value is exceeded and equal to or less than the second temperature threshold value, and the target SF number Nte is set to “2” when the temperature calculated value TE exceeds the second temperature threshold value. .

  Further, the target SF number determination circuit 45 determines the number of target subfields according to the power calculation value PE based on the notified power threshold value Pth, and outputs it as the target SF number Npe corresponding to the power calculation value PE. To do. Specifically, like the target SF number determination circuit 44, the target SF number determination circuit 45 is notified of one or more power threshold values Pth for the power calculation value PE. Then, the target SF number determination circuit 45 compares the calculated power value PE notified for each field with the power threshold value Pth, and determines whether or not the calculated power value PE exceeds a power threshold value Pth indicating a predetermined power. The target SF number determination circuit 45 determines the number of target subfields based on the determination result.

  The maximum value detector 433 detects and detects the larger value of the target SF number Nte determined by the target SF number determination circuit 44 and the target SF number Npe determined by the target SF number determination circuit 45. The obtained numerical value is set as the reduction target SF number Nsf. The maximum value detector 433 notifies the second image conversion unit 42 of such a reduction target SF number Nsf as conversion control data. With such a configuration, the conversion control data generation unit 43 performs an operation of writing the larger one of the target SF number Nte based on temperature and the target SF number Npe based on power consumption in order from the subfield with the smallest luminance weight. The number of subfields not to be subjected to, that is, the number of SFs to be reduced Nsf that is the number of SFs to be reduced, is notified to the second image conversion unit 42 as conversion control data indicating the number of SFs to be reduced Nsf.

  In this way, the second image conversion unit 42 does not perform the write operation from the subfield having the smallest luminance weight according to the number of subfields indicated by the notified conversion control data, that is, the number of SFs Nsf to be reduced. Set the number of. Then, the second image conversion unit 42 converts the image data according to the predetermined coding as shown in FIG. 5A based on the set number of subfields not performing the writing operation, for example, in FIGS. 5B and 5C. It changes to the image data by the coding as shown, that is, the image data that reduces the power consumption of the data electrode driving circuit 52. Thus, the image signal conversion circuit 40 changes the image data to reduce the power consumption of the data electrode driving circuit 52 in at least one subfield.

  As described above, the conversion control data generation unit 43 of the image signal conversion circuit 40 determines when at least the power consumption of the data electrode driving circuit 52 exceeds a predetermined power threshold and when the temperature exceeds a predetermined temperature threshold. The generated reduction target SF number Nsf is notified to the second image conversion unit 42 as conversion control data. The second image conversion unit 42 converts the image data into image data that reduces the power consumption of the data electrode driving circuit 52 based on such conversion control data.

  7A, 7B, 7C, and 7D are diagrams illustrating an example of an operation for generating conversion control data based on the calculated power value PE and the calculated temperature value TE of the plasma display device according to the first exemplary embodiment of the present invention. Hereinafter, an operation for adaptively controlling the power consumption of the data electrode driving circuit 52 in accordance with an image signal with the configuration shown in FIG. 6 will be described with reference to FIGS. 7A, 7B, 7C, and 7D. Here, an example will be described in which the number of all subfields is 10 and the number of subfields to be reduced can be changed from 1 to 8. That is, the first SF to the tenth SF as shown in FIG. 5A are set as subfields, and the write operation is performed with the first SF having the smallest luminance weight as shown in FIG. 5B according to the conversion control data. The change control is performed from no coding to coding in which the writing operation of the first SF to the eighth SF is not performed. Specifically, in the conversion control data, when the reduction target SF number Nsf is “0”, all subfields are subject to the write operation, and when the reduction target SF number Nsf is “1”, the first SF is the reduction target. As an example of the reduction target SF number Nsf, when the reduction target SF number Nsf is “8”, an example is given in which the first to eighth SFs are targeted for reduction.

  FIG. 7A shows a change in the calculated power value PE and the calculated temperature value TE when a normal image signal and an image signal that consumes a large amount of power in the data electrode driving circuit 52 are input as in a checkered pattern image. An example is shown. FIG. 7A shows a case where a normal image signal is input until time t1, a checkered image signal is input from time t1 to time t4, and the normal image signal is restored after time t4. ing.

  In FIG. 7A, the target SF number determining circuit 44 determines the target SF number Nte for the temperature calculated value TE, and the temperature minimum threshold Tth_max and the temperature minimum threshold Tth_min, and the target SF number determining circuit 45 is for the power calculated value PE. The maximum power threshold Pth_max and the minimum power threshold Pth_min for determining the target SF number Npe are shown. That is, here, an example is given in which the number of subfields to be reduced is “8”, and according to this, the conversion control data generation unit 43 has eight different values of the temperature threshold Tth and eight different values. The value power threshold value Pth is stored. According to this number, the target SF number determination circuit 44 sets the target SF number Nte to “0” when the temperature calculated value TE is equal to or lower than the temperature minimum threshold Tth_min, and the temperature calculated value TE exceeds the temperature minimum threshold Tth_min. When the value is smaller than the small threshold, the target SF number Nte is output as “1”. Then, the target SF number determination circuit 44 sequentially increases the target SF number Nte according to each threshold value, and outputs the target SF number Nte as “8” when the temperature calculation value TE exceeds the temperature maximum threshold value Tth_max. Similarly, the target SF number determination circuit 45 sets the target SF number Npe to “0” when the power calculation value PE is equal to or smaller than the power minimum threshold Pth_min, and the power calculation value PE exceeds the power minimum threshold Pth_min and is the next smallest. If it is equal to or less than the threshold, the target SF number Npe is output as “1”. Then, the target SF number determination circuit 45 sequentially increases the target SF number Npe according to each threshold, and outputs the target SF number Npe as “8” when the power calculation value PE exceeds the power maximum threshold Pth_max.

  FIG. 7B shows the target SF number Npe determined by the target SF number determination circuit 45 based on the power calculation value PE shown in FIG. 7A. FIG. 7C shows the target SF number Nte determined by the target SF number determination circuit 44 based on the calculated temperature value TE shown in FIG. 7A. FIG. 7D illustrates the reduction target SF number Nsf, which is the larger number detected by the maximum value detector 433 among the target SF number Npe and the target SF number Nte.

  First, in the period up to time t1 in FIGS. 7A, 7B, 7C, and 7D, since a normal image signal is input, the relationship between the light emission states between adjacent discharge cells is random. For this reason, the power consumption of each drive IC 521 does not increase extremely, and the number of changes in the address pulse voltage between adjacent discharge cells detected by each load calculation circuit 601 does not increase extremely. The output load value is also an average load value, for example.

  For this reason, as shown in FIG. 7A, the power calculation value PE output from the power calculation circuit 62 is equal to or less than the minimum power threshold Pth_min in the target SF number determination circuit 45. As a result, as shown in FIG. 7B, during the period up to time t1, the target SF number determination circuit 45 outputs the target SF number Npe as “0”. Similarly, the temperature calculation value TE output from the temperature calculation circuit 61 is equal to or lower than the temperature minimum threshold value Tth_min in the target SF number determination circuit 44. As a result, as shown in FIG. 7C, in the period up to time t1, the target SF number determination circuit 44 also outputs the target SF number Nte as “0”. Since the maximum value detector 433 is equal to both the target SF number Npe and the target SF number Nte during the period up to time t1, the maximum value detector 433 One value of the target SF number Npe and the target SF number Nte is selected, and conversion control data that sets the reduction target SF number Nsf to “0” as shown in FIG. 7D is output.

  The second image conversion unit 42 receives the conversion control data in which the number of SFs to be reduced Nsf is “0”, and based on this, sets all the subfields as the target of the write operation. That is, when the reduction target SF number Nsf is “0”, the second image conversion unit 42 does not change the image data generated by the first image conversion unit 41 according to the predetermined coding as illustrated in FIG. Each block is supplied to each drive IC 521 of the data electrode drive circuit 52. When the normal image signal is supplied as described above, the plasma display device of the present embodiment performs display using all the set subfields by performing the above-described operation. Process.

  Next, when a checkered pattern image signal is input such that the relationship between the light emitting states between adjacent discharge cells is reversed in the period from time t1 to time t4 shown in FIGS. 7A, 7B, 7C, and 7D. Will be described. When such an image signal is input, as described above, the number of changes in the write pulse voltage increases, and thereby the power consumption of each drive IC 521 also increases. Since each load calculation circuit 601 detects the increased number of changes in this way, the load value output from each load calculation circuit 601 also increases rapidly. For this reason, as shown in FIG. 7A, from time t1 to time t2, the power calculation value PE output from the power calculation circuit 62 also increases rapidly, exceeding the power maximum threshold Pth_max in the target SF number determination circuit 45. Become. As a result, as shown in FIG. 7B, in the period from time t1 to time t2, the target SF number determination circuit 45 outputs the target SF number Npe having values of “1”, “3”, and “8” in order. To do.

  On the other hand, each cumulative calculator 611 in the temperature calculation circuit 61 cumulatively calculates the load value output from the load calculation circuit 601, and therefore, as shown in FIG. 7A, the temperature calculation value TE suddenly increases after time t1. It increases slowly without increasing. Therefore, as shown in FIG. 7C, during the period from time t1 to time t2, the target SF number determination circuit 44 outputs the target SF number Nte having a value such as “0”.

  The maximum value detector 433 detects the larger number of the target SF number Npe and the target SF number Nte. Therefore, as shown in FIG. 7D, in the period from time t1 to time t2, the maximum value detector 433 selects the number of target SFs Npe and sequentially reduces it to “1” “3” “8”. Conversion control data indicating the SF number Nsf is output. Since the second image conversion unit 42 receives conversion control data in which the reduction target SF number Nsf is sequentially set to “1”, “3”, and “8”, the second image conversion unit 42 performs the write operation for the number of subfields based on the reduction target SF number Nsf. Change to image data that stops. That is, when the reduction target SF number Nsf is “1”, the second image conversion unit 42 sets the first SF as a reduction target, and does not perform the first SF writing operation on the image data supplied from the first image conversion unit 41. Convert to image data changed to coding. Similarly, when the reduction target SF count Nsf is “3”, the first SF to the third SF are targeted for reduction, and the image data supplied from the first image conversion unit 41 is not subjected to the writing operation of the first SF to the third SF. Convert to image data changed to coding. When the number of SFs to be reduced Nsf is “8”, the second image conversion unit 42 sets the image data supplied from the first image conversion unit 41 to the first SF to the first SF with the first SF to the eighth SF as reduction targets. It is converted into image data that has been changed to coding that does not perform the 8SF writing operation. In this way, when an image signal whose power consumption increases abruptly is input, the second image conversion unit 42 responds to the power consumption that increases rapidly by feedback control via the power calculation circuit 62. Changes to image data that rapidly reduces power consumption.

  As shown in FIG. 7A, in the period from time t1 to time t2, the feedback control via the power calculation circuit 62 makes it possible to reduce power consumption rapidly from the first SF to the eighth SF. Therefore, the power consumption of each drive IC 521 that has risen suddenly operates to decrease from around time t2. That is, from time t2 to time t3, the feedback control operation via the power calculation circuit 62 continues, and the power consumption of each drive IC 521 and the power calculation value PE gradually decrease accordingly. Then, the target SF number Npe gradually decreases to “6” and “5” as shown in FIG. 7B.

  On the other hand, due to the increase in power consumption accompanying the change of the image signal from time t1, the temperature of each drive IC 521 gradually increases from around time t2, and the calculated temperature value TE gradually increases accordingly. For this reason, as shown in FIG. 7A, the temperature calculation value TE exceeds the temperature minimum threshold value Tth_min in the target SF number determination circuit 45. As a result, as shown in FIG. 7C, the target SF number determination circuit 44 sequentially sets “1”, “2”, and “3” to the target SF number Nte from the middle of the period from time t2 to time t3. Is output.

  When the target SF number Npe and the target SF number Nte are compared in the period from time t2 to time t3, as shown in FIGS. 7B and 7C, the target SF number Npe is still larger in this period. Therefore, the maximum value detector 433 selects the target SF number Npe which is the larger number even during the period from the time t2 to the time t3, and sequentially “6” “5” “4” as illustrated in FIG. 7D. Conversion control data indicating the number of SFs Nsf to be reduced, such as “ Further, the second image conversion unit 42 outputs image data in which writing of the target subfield is stopped according to the number of SFs Nsf to be reduced. As described above, even after an image signal whose power consumption is rapidly increased is input, each drive IC 521 is controlled by feedback control via the power calculation circuit 62 during a period from time t2 to time t3. An operation is performed to gradually reduce the power consumption.

  Further, during the period from time t3 to time t4, the power consumption, the power calculation value PE, and the target SF number Npe of each drive IC 521 are stabilized to a substantially constant value by the feedback control as described above. On the other hand, the temperature of each drive IC 521 continues to increase gradually for a while after time t3 due to an increase in power consumption from time t1. Along with this, the temperature calculation value TE and the target SF number Nte also gradually increase. For this reason, as shown in FIGS. 7B and 7C, after time t3, the target SF number Nte is larger than the target SF number Npe, and the maximum value detector 433 selects the target SF number Nte. As shown in 7D, conversion control data indicating the number of SFs Nsf to be reduced, such as “5”, “6”, and “5”, is output in order.

  Further, the second image conversion unit 42 outputs image data in which writing of the target subfield is stopped according to the number of SFs Nsf to be reduced. In this way, after a certain time has elapsed after an image signal that increases power consumption is input, the control shifts to feedback control via the temperature calculation circuit 61, and the temperature rises together with the power consumption of each drive IC 521. An operation that suppresses this is executed. In addition, like the conversion control data generation part 43, it is set as the structure which calculates | requires the larger value among the target SF number Npe based on power consumption, and the target SF number Nte based on temperature by the maximum value detector 433. Accordingly, the power consumption of each drive IC 521 can be suppressed based on at least one of the power consumption and the temperature, and the feedback control for each of the power consumption and the temperature can be switched with a simple configuration.

  As described above, when an image signal that increases the power consumption in the data electrode driving circuit 52 is input during the period from the time t1 to the time t4, the plasma display device according to the present embodiment starts with the power calculation circuit. By the feedback control that suppresses the power consumption via 62, it responds immediately to the increase in power consumption and operates to rapidly reduce the power consumption. Then, the plasma display device responds to the gradually increasing temperature by feedback control that suppresses the temperature increase via the temperature calculation circuit 61 so as to suppress the temperature increase along with the power consumption. Operate. For this reason, when an image signal that increases power consumption is input, for example, compared with a method of lowering the temperature of the data electrode drive circuit by temperature feedback control, the plasma display device of the present embodiment is The power consumption is immediately suppressed, thereby suppressing the temperature rise.

  Further, when switching to a normal image at time t4, the number of changes in the write pulse voltage decreases, so the load value output from each load calculation circuit 601 also decreases. Along with this, the power calculation value PE and the target SF number Npe also decrease, and the temperature calculation value TE and the target SF number Nte also decrease slowly. Thereafter, when the number of SFs to be reduced Nsf is reduced to “0” in the conversion control data, the image signal conversion circuit 40 converts the image data according to the predetermined coding as shown in FIG. The image is supplied to each drive IC 521 of the drive circuit 52 and the panel 10 displays an image according to a predetermined coding that does not stop the subfield writing. As described above, when the coding is changed so that the power consumption of the data electrode driving circuit 52 is reduced, the number of displayable luminances is reduced. However, since the image signal that increases the power consumption of the data electrode driving circuit 52 is an image whose luminance changes greatly for each pixel or for each narrow area, even if the number of displayed luminances is reduced to some extent, Is hardly recognized.

  As described above, the plasma display device according to the present embodiment includes the power calculation circuit 62 that calculates the power consumption of the data electrode drive circuit 52 based on the image data, and the temperature of the data electrode drive circuit 52 based on the image data. And a temperature calculation circuit 61 for calculating. Then, the image signal conversion circuit 40 reduces the power consumption of the data electrode drive circuit 52 when the calculated power consumption exceeds a predetermined power threshold or when the calculated temperature exceeds a predetermined temperature threshold. Convert to image data.

  With such a configuration, the plasma display apparatus according to the present embodiment first performs feedback control via the power calculation circuit 62 that suppresses power consumption, such as when an image signal that increases power consumption is input. As a result, power consumption is rapidly reduced. Thereafter, the plasma display device suppresses the temperature rise together with the power consumption by feedback control that suppresses the temperature rise via the temperature calculation circuit 61. Therefore, according to the plasma display device of the present invention, it is possible to respond immediately to a rapid increase in power consumption, and to perform image display with stable operation without malfunction of the data electrode driving circuit. A plasma display device can be provided.

(Embodiment 2)
FIG. 8 is a circuit block diagram of the plasma display device in accordance with the second exemplary embodiment of the present invention. The plasma display device according to the present embodiment includes a panel 10, an image signal conversion circuit 400, a data electrode drive circuit 52, a scan electrode drive circuit 53, a sustain electrode drive circuit 54, a timing generation circuit 55, a data electrode load calculation circuit 60, a temperature. Temperature calculation circuit 61 as a calculation unit, power calculation circuit 62 as a power calculation unit, temperature change detection circuit 63 as a temperature change detection unit, power change detection circuit 64 as a power change detection unit, and power required for each circuit block A power supply circuit (not shown) is provided. In FIG. 8, the constituent elements having the same reference numerals as those in FIG. 4 have the same functions as those in FIG.

  In FIG. 8, an image signal conversion circuit 400 converts an input image signal into image data indicating light emission / non-light emission for each subfield, similar to the image signal conversion circuit 40 in the first embodiment. Further, the image signal conversion circuit 400 changes the coding based on the same conversion control data as in the first embodiment. In other words, the image signal conversion circuit 400 is a circuit that converts an image signal into image data for causing a discharge cell to emit light or not to emit light in each subfield period. In particular, in this conversion processing, the image signal conversion circuit 400 converts the image signal into the data electrode drive when at least the power consumption of the data electrode drive circuit 52 is greater than a predetermined power threshold and when the temperature is greater than the predetermined temperature threshold. Conversion to image data that reduces the power consumption of the circuit 52 is performed.

  The image signal conversion circuit 400 supplies the image data generated as described above to the data electrode driving circuit 52. The data electrode driving circuit 52 converts the image data for each subfield into signals corresponding to the data electrodes D1 to Dm, and drives the data electrodes D1 to Dm, respectively.

  The image data generated by the image signal conversion circuit 400 is also supplied to the data electrode load calculation circuit 60. The data electrode load calculation circuit 60 calculates the load amount in each field of the data electrode drive circuit 52 by calculation.

  The temperature calculation circuit 61 calculates the temperature in the data electrode drive circuit 52 by further performing arithmetic processing on the load value calculated by the data electrode load calculation circuit 60. In addition, the power calculation circuit 62 calculates the power consumption in the data electrode drive circuit 52 by further performing arithmetic processing on the load value calculated by the data electrode load calculation circuit 60. Thus, the temperature calculation circuit 61 calculates the temperature in the data electrode drive circuit 52 based on the image data output from the image signal conversion circuit 400, and the power calculation circuit 62 is output from the image signal conversion circuit 400. The power consumption in the data electrode driving circuit 52 is calculated based on the obtained image data.

  The temperature calculation circuit 61 notifies the image signal conversion circuit 400 and the temperature change detection circuit 63 of the calculated temperature as a temperature calculation value TE. The power calculation circuit 62 notifies the calculated power consumption to the image signal conversion circuit 400 and the power change detection circuit 64 as a power calculation value PE.

  The temperature change detection circuit 63 detects, for each field, a temperature change direction indicating whether the temperature calculation value TE has increased or decreased based on the notified temperature calculation value TE, and the image signal conversion circuit as a temperature change direction signal Swt. 400 is notified. Further, the power change detection circuit 64 detects, for each field, a power change direction indicating whether the power calculated value PE has increased or decreased based on the notified power calculated value PE, and an image signal as the power change direction signal Swp. The conversion circuit 400 is notified. Although details will be described below, in order to control power consumption in the data electrode driving circuit 52, the image signal conversion circuit 400 has a larger temperature calculation value TE than the temperature threshold value that is changed according to the temperature change direction signal Swt. The above-described conversion control data is generated based on whether or not the power calculation value PE is larger than the power threshold value that is changed according to the power change direction signal Swp.

  That is, the image signal conversion circuit 400 has a first temperature threshold value as a temperature threshold value, a second temperature threshold value smaller than the first temperature threshold value, and a first power threshold value and a first power threshold value as power threshold values. It has a small second power threshold. Then, based on these threshold values, the image signal conversion circuit 400 determines whether the temperature calculation value TE and the power calculation value PE have exceeded these threshold values or become below, and generates conversion control data based on this determination. To do. As described above, the plasma display device according to the present embodiment includes the temperature change detection circuit 63 that detects the temperature change direction of whether the temperature calculation value TE rises or falls per unit time, and the power calculation value PE includes the unit time. And a power change detection circuit 64 that detects a power change direction that rises or falls. The image signal conversion circuit 400 outputs the image signal to the data electrode driving circuit 52 at least when the power calculation value PE exceeds the first power threshold value or when the temperature calculation value exceeds the first temperature threshold value. A feature is that the image data is converted into image data that reduces power consumption. Further, the image signal conversion circuit 400 outputs the image signal to the data electrode drive when at least the power calculation value PE is equal to or lower than the second power threshold value or when the temperature calculation value TE is equal to or lower than the second temperature threshold value. The circuit 52 is characterized in that it is converted into image data that increases power consumption.

  In the present embodiment, the plasma display device will be described with reference to a configuration example in which each of the temperature change detection circuit 63 and the power change detection circuit 64 is provided. However, the plasma display device may be configured to include either one of the temperature change detection circuit 63 and the power change detection circuit 64 and change the corresponding temperature or power threshold according to the change direction. That is, at least when the power calculation value PE exceeds a predetermined power threshold value, or when the temperature calculation value exceeds the first temperature threshold value, the plasma display device displays the image signal and the power consumption of the data electrode driving circuit 52. A configuration may be adopted in which the image data is reduced. In addition, the plasma display device outputs an image signal to the data electrode driving circuit 52 at least when the power calculation value PE is equal to or lower than the predetermined power threshold value or when the temperature calculation value TE is equal to or lower than the second temperature threshold value. The image data may be converted into image data that increases the power consumption. Alternatively, the plasma display device at least calculates the power consumption of the data electrode driving circuit 52 when the power calculation value PE exceeds the first power threshold or when the temperature calculation value exceeds a predetermined temperature threshold. A configuration may be adopted in which the image data is reduced. In addition, the plasma display device outputs an image signal to the data electrode driving circuit 52 at least when the calculated power value PE is equal to or lower than the second power threshold value or when the calculated temperature value TE is equal to or lower than the predetermined temperature threshold value. The image data may be converted into image data that increases power consumption. In the present embodiment, the plasma display device is described as a configuration in which the temperature change detection circuit 63 and the power change detection circuit 64 detect changes for each field. For example, the plasma display device detects changes for every several fields. Any configuration may be used as long as it detects whether the temperature and power increase or decrease per unit time.

  The image signal conversion circuit 400 generates conversion control data for controlling the conversion of the image signal based on the temperature calculation value TE, the temperature change direction signal Swt, the power calculation value PE, and the power change direction signal Swp notified as described above. Then, the image data generated by the coding based on the conversion control data is output.

  With the configuration as described above, in the plasma display device of the present embodiment, the power calculation circuit 62 calculates the power consumption of the data electrode driving circuit 52 based on the image data output from the image signal conversion circuit 400, and the temperature The calculation circuit 61 calculates the temperature of the data electrode drive circuit 52. The temperature change detection circuit 63 detects the temperature change direction per unit time, and the power change detection circuit 64 detects the power change direction per unit time. Furthermore, the image signal conversion circuit 400 generates conversion control data based on the calculated power consumption and temperature by using the temperature threshold corresponding to the temperature change direction and the power threshold corresponding to the power change direction. If it is determined that at least one of the power consumption and temperature of the data electrode driving circuit 52 has increased based on this conversion control data, the coding is changed to a coding that does not perform an address operation in a subfield with a small luminance weight. The plasma display apparatus according to the present embodiment executes such feedback processing, and thus adaptively controls power consumption according to the image signal.

  Next, a more detailed configuration for adaptively controlling power consumption in the plasma display device of the present embodiment will be described. FIG. 9 is a circuit block diagram showing a detailed configuration example of the main part of the circuit configuration for controlling the power consumption of the plasma display device in accordance with the second exemplary embodiment of the present invention. Here, as in the first embodiment, the data electrode driving circuit 52 is configured by an IC as a driving unit which is a plurality of driving integrated circuits. The data electrode driving circuit 52 will be described with an example in which the data electrode driving circuit 52 has a plurality of driving units respectively corresponding to the data electrodes 32 of the panel 10 divided into blocks. FIG. 9 shows an example in which there are four such drive ICs 521 included in the data electrode drive circuit 52 and the power consumption and temperature are calculated for each drive IC 521. In FIG. 9, the components given the same reference numerals as those in FIG. 6 have the same functions as those in FIG. 6, and detailed description thereof will be omitted.

  As illustrated in FIG. 9, the image signal conversion circuit 400 includes a first image conversion unit 41, a second image conversion unit 42, and a conversion control data generation unit 46. The first image conversion unit 41 converts the supplied image signal into image data indicating light emission / non-light emission for each subfield according to a predetermined coding. In addition, the second image conversion unit 42 performs coding in which image data according to predetermined coding is not written in a subfield with a small luminance weight according to the conversion control data notified from the conversion control data generation unit 46. Change to image data. Further, the conversion control data generation unit 46 generates conversion control data for such change control.

  In FIG. 9, the temperature change detection circuit 63 uses, for example, the current temperature calculation value TE and the temperature calculation value TE notified one field before the temperature calculation value TE notified from the temperature calculation circuit 61. Compare. Then, the temperature change detection circuit 63 determines whether the calculated temperature value TE has increased or decreased by this comparison. In addition, the temperature change detection circuit 63 notifies the image signal conversion circuit 400 of the determination result as a temperature change direction signal Swt. In addition, the power change detection circuit 64 compares, for example, the current power calculation value PE and the power calculation value PE notified one field before the power calculation value PE notified from the power calculation circuit 62. The power change detection circuit 64 determines whether the power calculation value PE has increased or decreased by this comparison. In addition, the power change detection circuit 64 notifies the image signal conversion circuit 400 of the determination result as the power change direction signal Swp.

  The temperature calculation value TE from the temperature calculation circuit 61, the temperature change direction signal Swt from the temperature change detection circuit 63, the power calculation value PE from the power calculation circuit 62, and the power change direction signal Swp from the power change detection circuit 64 are images. This is notified to the conversion control data generation unit 46 of the signal conversion circuit 400. The conversion control data generation unit 46 includes a target SF number determination circuit 47 that determines the number of subfields according to the temperature calculation value TE, and a target SF number determination circuit 48 that determines the number of subfields according to the power calculation value PE. And a maximum value detector 433 that detects and outputs the maximum value among the output values of the target SF number determination circuit 47 and the target SF number determination circuit 48. Note that the number of subfields determined by the target SF number determination circuit 47 and the target SF number determination circuit 48 corresponds to the number of subfields in which no write operation is performed.

  The conversion control data generation unit 46 also includes a temperature threshold value Tthu as a first temperature threshold value indicating a predetermined temperature value, a temperature threshold value Tthd as a second temperature threshold value, and a first power value indicating a predetermined power value. A power threshold Pthu as a power threshold and a power threshold Pthd as a second power threshold are stored. The target SF number determination circuit 47 is notified of the temperature threshold Tthu and the temperature threshold Tthd. The temperature threshold value Tthu and the temperature threshold value Tthd are temperature threshold values provided for selecting one of the values according to the temperature change direction based on the temperature calculation value TE. The temperature threshold Tthu is selected when the temperature rises, and the temperature threshold Tthd is selected when the temperature falls. Further, the temperature threshold value Tthu is set to a larger value than the temperature threshold value Tthd. On the other hand, the target SF number determination circuit 48 is notified of the power threshold Pthu and the power threshold Pthd. The power threshold value Pthu and the power threshold value Pthd are power threshold values provided for selecting one of the values in accordance with the direction of change of power based on the calculated power value PE. The power threshold Pthu is selected when the power increases, and the power threshold Pthd is selected when the power decreases. Also, the power threshold value Pthu is set to a larger value than the power threshold value Pthd.

  The target SF number determination circuit 47 of the conversion control data generation unit 46 first selects one of the temperature threshold value Tthu and the temperature threshold value Tthd according to the notified temperature change direction signal Swt. The target SF number determination circuit 47 selects the temperature threshold Tth when the temperature calculation value TE is notified by the temperature change direction signal Swt, and selects the temperature threshold Tthd when the temperature calculation value TE is notified. select.

  Next, the target SF number determining circuit 47 determines the number of target subfields based on the temperature threshold value Tth that is the selected threshold value, and outputs it as the target SF number Nte. That is, when the target SF number determining circuit 47 determines the target SF number Nte, which is the number of subfields according to the temperature calculated value TE, the target SF number Nte is calculated according to the temperature change direction. The target SF number Nte is determined based on a determination method having hysteresis characteristics with different correspondences. Specifically, the target SF number determination circuit 47 is notified of a temperature threshold value Tthu and a temperature threshold value Tthd that are one or more combinations with respect to the temperature calculation value TE. Then, the target SF number determination circuit 47 compares the temperature calculation value TE notified for each field with a temperature threshold value Tth having a value corresponding to the change direction of the temperature, and the temperature calculation value TE indicates a predetermined temperature. It is determined whether or not the threshold value Tth is exceeded. The target SF number determination circuit 47 determines the number of target subfields based on the determination result.

  FIG. 10A is a diagram showing an example of a temperature threshold Tthu and a temperature threshold Tthd set to determine the target SF number Nte in Embodiment 2 of the present invention. Here, an example is given in which the number of target SFs Nte is changed from 0 to 8. Along with this, a temperature threshold value Tthu and a temperature threshold value Tthd, which are eight combinations, are set. In FIG. 10A, the solid line indicates the temperature threshold value Tthu corresponding to the temperature rise, and among these, the threshold value in eight steps from the lowest temperature minimum threshold value Tthu_min to the highest value temperature maximum threshold value Tthu_max is shown. . The broken line indicates the temperature threshold value Tthd corresponding to the temperature drop, and shows eight threshold values from the lowest temperature minimum threshold value Tthd_min to the highest temperature maximum threshold value Tthd_max among them.

  For example, when the temperature calculation value TE rises with respect to such a temperature threshold value, the target SF number determination circuit 47 first sets the target SF number Nte as “the target SF number Nte” when the temperature calculation value TE is equal to or lower than the temperature threshold value Tthu_min. "0" is output. When the temperature calculation value TE exceeds the temperature threshold value Tthu_min as the temperature calculation value TE rises, the target SF number determination circuit 47 next outputs “1” as the target SF number Nte. Similarly, the target SF count determining circuit 47 sequentially outputs the target SF count Nte corresponding to the set temperature threshold value Tth shown in FIG.

  On the other hand, for example, when the temperature calculation value TE decreases, the target SF number determination circuit 47 first sets “8” as the target SF number Nte when the temperature calculation value TE exceeds the temperature threshold value Tthd_max. Output. When the temperature calculation value TE becomes equal to or lower than the temperature threshold value Tthd_max as the temperature calculation value TE decreases, the target SF number determination circuit 47 next outputs “7” as the target SF number Nte. Similarly, the target SF number determination circuit 47 outputs the target SF number Nte corresponding to the set temperature threshold value Tthd shown in FIG.

  The target SF number determination circuit 48 first selects either the power threshold Pthu or the power threshold Pthd according to the notified power change direction signal Swp. The target SF number determination circuit 48 selects the power threshold Pthu when it is notified by the power change direction signal Swp that the power calculation value PE has increased. Further, the target SF number determination circuit 48 selects the power threshold value Pthd when notified that the power calculation value PE has dropped.

  Next, the target SF number determination circuit 48 determines the number of target subfields based on the selected power threshold value Pth, which is a selected threshold value, and outputs it as the target SF number Npe. That is, the target SF number determination circuit 48 has a hysteresis characteristic according to the change direction of the power calculation value PE, and outputs the change direction of the power calculation value PE and the target SF number Npe corresponding to the value. Specifically, similarly to the target SF number determination circuit 47, the target SF number determination circuit 48 is notified of the power threshold value Pthu and the power threshold value Pthd, which are one or more combinations with respect to the calculated power value PE. The target SF number determination circuit 48 compares the power calculation value PE notified for each field with the power threshold value Pth having a value corresponding to the change direction of the power, and sets the power threshold value Pth at which the power calculation value PE indicates predetermined power. Determine if it has exceeded. The target SF number determination circuit 48 determines the number of target subfields based on the determination result.

  FIG. 10B is a diagram showing an example of the power threshold value Pthu and the power threshold value Pthd set to determine the target SF number Npe, which is the number of target subfields according to Embodiment 2 of the present invention. Here, as well as the target SF number Nte, an example is given in which the number of target SF numbers Npe is changed from 0 to 8. Along with this, a power threshold value Pthu and a power threshold value Pthd, which are eight combinations, are set. In FIG. 10B, the solid line indicates the power threshold value Pthu corresponding to the power increase, and among the threshold values of eight levels from the lowest power minimum threshold value Pthu_min to the highest power maximum threshold value Pthu_max among them. . A broken line indicates a power threshold value Pthd corresponding to the power decrease, and indicates eight threshold values from a minimum power minimum threshold value Pthd_min to a maximum power maximum threshold value Pthd_max among them.

  Similarly to the target SF number determination circuit 47, the target SF number determination circuit 48 corresponds to the set power threshold value Pth shown in FIG. 10B as the power calculation value PE sequentially increases. The number of target SFs Npe to be output is output. Further, the target SF number determination circuit 48 outputs the target SF number Npe corresponding to the set power threshold value Pthd shown in FIG. 10B as the power calculation value PE sequentially decreases.

  The maximum value detector 433 detects and detects the larger value of the target SF number Nte determined by the target SF number determination circuit 47 and the target SF number Npe determined by the target SF number determination circuit 48. The obtained numerical value is set as the reduction target SF number Nsf. The maximum value detector 433 notifies the second image conversion unit 42 of this reduction target SF number Nsf as conversion control data. With such a configuration, the conversion control data generation unit 46 writes the larger number of the target SF number Nte based on temperature and the target SF number Npe based on power consumption in order from the subfield with the smallest luminance weight. It is assumed that the number of subfields not to be subjected to, that is, the number of SFs to be reduced Nsf, which is the number of SFs to be reduced. Then, the conversion control data generation unit 46 notifies the second image conversion unit 42 of the SF number Nsf to be reduced as conversion control data.

  In this way, the second image conversion unit 42 does not perform the write operation from the subfield having the smallest luminance weight according to the number of subfields indicated by the notified conversion control data, that is, the number of SFs Nsf to be reduced. Set the number of. Then, the image data according to the predetermined coding as shown in FIG. 5A, for example, the image data by the coding as shown in FIGS. 5B and 5C, that is, the power consumption of the data electrode driving circuit 52 is reduced. Change to the correct image data.

  As described above, the conversion control data generation unit 46 of the image signal conversion circuit 400 has at least a case where the power consumption of the data electrode driving circuit 52 exceeds or falls below a predetermined power threshold corresponding to the direction of power change, or the temperature. The reduction target SF number Nsf generated by the determination when the predetermined temperature threshold value according to the temperature change direction is exceeded or when it is below is notified to the second image conversion unit 42 as conversion control data. Then, the second image conversion unit 42 converts the image data into image data that reduces or increases the power consumption of the data electrode driving circuit 52 based on the conversion control data.

  11A, 11B, 11C, and 11D are diagrams illustrating an example of an operation for generating conversion control data based on the calculated power value PE and the calculated temperature value TE of the plasma display device according to the second exemplary embodiment of the present invention. Hereinafter, an operation of adaptively controlling the power consumption of the data electrode driving circuit 52 according to an image signal with the configuration shown in FIG. 9 will be described with reference to FIGS. 11A, 11B, 11C, and 11D. Here, as in FIGS. 7A, 7B, 7C, and 7D, an example is given in which the number of all subfields is set to 10 and the number of subfields to be reduced can be changed from 1 to 8. explain.

  That is, the first SF to the 10th SF as shown in FIG. 5A are set as subfields, and the writing operation is not performed with the first SF having the smallest luminance weight shown in FIG. 5B according to the conversion control data. To the change control from the first SF to the eighth SF in which the writing operation is not performed. Specifically, in the conversion control data, when the reduction target SF number Nsf is “0”, all subfields are subject to the write operation, and when the reduction target SF number Nsf is “1”, the first SF is set as the reduction target. To do. An example in which the first SF to the eighth SF are targeted for reduction when the number of reduction target SFs Nsf is “8” as the number of reduction target SFs Nsf sequentially increases is given. Further, the reduction target SF number Nsf is determined based on the characteristic of the target SF number Nte shown in FIG. 10A with respect to the temperature calculation value TE and the characteristic of the target SF number Npe shown in FIG. 10B with respect to the power calculation value PE. explain.

  FIG. 11A shows a change in the calculated power value PE and the calculated temperature value TE when a normal image signal and an image signal that consumes a large amount of power in the data electrode drive circuit 52 are input as in a checkered pattern image. An example is shown. FIG. 11A shows a case where a normal image signal is input until time t1, a checkered image signal is input from time t1 to time t4, and the normal image signal is restored after time t4. .

  Further, FIG. 11A shows the maximum temperature threshold value Tthu_max and the minimum temperature threshold value Tthu_min, and the maximum temperature threshold value Tthd_max and the minimum temperature threshold value Tthd_min by which the target SF number determination circuit 47 determines the target SF number Nte with respect to the temperature calculation value TE. . The maximum temperature threshold value Tthu_max and the minimum temperature threshold value Tthu_min correspond to the temperature increasing direction, and the maximum temperature threshold value Tthd_max and the minimum temperature threshold value Tthd_min correspond to the temperature decreasing direction. Furthermore, in FIG. 11A, the maximum power threshold Pth_max and the minimum power threshold Pth_min, and the maximum power threshold Pthd_max and the minimum power threshold Pthd_min, in which the target SF number determination circuit 48 determines the target SF number Npe for the power calculation value PE are shown. . The power maximum threshold Pthu_max and the power minimum threshold Pthu_min correspond to the direction in which the power increases, and the power maximum threshold Pthd_max and the power minimum threshold Pthd_min correspond to the direction in which the power decreases.

  That is, an example is given here in which the number of subfields to be reduced is set to “8”. Accordingly, the conversion control data generation unit 46 stores a temperature threshold Tth as shown in FIG. 10A and a power threshold Pth as shown in FIG. 10B. In accordance with this number, for example, when the temperature rises, the target SF number determination circuit 47 sets the target SF number Nte to “0” when the temperature calculation value TE is equal to or lower than the temperature minimum threshold Tthu_min, and calculates the temperature calculation value TE. Exceeds the minimum temperature threshold value Tthu_min and is equal to or smaller than the next smallest threshold value, the target SF number Nte is set to “1”. Then, the target SF number determination circuit 47 sequentially increases the target SF number Nte according to each threshold value, and outputs the target SF number Nte as “8” when the temperature calculation value TE exceeds the temperature maximum threshold value Tthu_max. Similarly, for example, when the power is increasing, the target SF number determination circuit 48 sets the target SF number Npe to “0” when the power calculation value PE is equal to or less than the power minimum threshold Pthu_min, and the power calculation value PE is When the power minimum threshold value Pthu_min is exceeded and is equal to or smaller than the next smallest threshold value, the target SF number Npe is set to “1”. Then, the target SF number determining circuit 48 sequentially increases the target SF number Npe according to each threshold value, and outputs the target SF number Npe as “8” when the power calculation value PE exceeds the power maximum threshold value Pthu_max.

  FIG. 11B shows the target SF number Npe determined by the target SF number determination circuit 48 based on the power calculation value PE shown in FIG. 11A. FIG. 11C shows the target SF number Nte determined by the target SF number determination circuit 47 based on the calculated temperature value TE shown in FIG. 11A. FIG. 11D illustrates the reduction target SF number Nsf that is the larger number detected by the maximum value detector 433 among the target SF number Npe and the target SF number Nte.

  First, in the period up to time t1 in FIGS. 11A, 11B, 11C, and 11D, since a normal image signal is input, the relationship between light emission states between adjacent discharge cells is random. For this reason, the power consumption of each drive IC 521 does not increase extremely, and the number of changes in the address pulse voltage between adjacent discharge cells detected by each load calculation circuit 601 does not increase extremely. The output load value is also an average load value, for example.

  For this reason, as shown in FIG. 11A, the power calculation value PE output from the power calculation circuit 62 may exceed the power minimum threshold Pthd_min in the power decrease direction in the target SF number determination circuit 48, but in the power increase direction. It becomes below the electric power minimum threshold Pthu_min. That is, the target SF number Npe is “0” because it is equal to or smaller than the power minimum threshold Pthu_min in the direction of increasing power. Further, since the electric power decreases in the direction in which the electric power decreases, the target SF number Npe is “0” in this case as well. As a result, as shown in FIG. 11B, during the period up to time t1, the target SF number determination circuit 48 outputs the target SF number Npe as “0”.

  Similarly, the temperature calculation value TE output from the temperature calculation circuit 61 may exceed the temperature minimum threshold value Tthd_min in the temperature decreasing direction in the target SF number determination circuit 47, but is below the temperature minimum threshold value Tthu_min in the temperature increasing direction. . That is, the target SF number Nte is “0” because it is equal to or lower than the temperature minimum threshold value Tthu_min in the direction in which the temperature rises. In addition, since the temperature falls below the minimum temperature threshold value Tthd_min in the direction in which the temperature decreases, the target SF number Nte is “0” in this case as well. As a result, as shown in FIG. 11C, in the period up to time t1, the target SF number determination circuit 47 also outputs the target SF number Nte as “0”.

  In the maximum value detector 433, during the period up to time t1, both the target SF number Npe and the target SF number Nte are “0” and are equal. Therefore, in such a case, the maximum value detector 433 selects one of the target SF number Npe and the target SF number Nte, and sets the reduction target SF number Nsf to “0” as shown in FIG. 11D. The conversion control data is output. The second image conversion unit 42 receives the conversion control data in which the number of SFs to be reduced Nsf is “0”, and based on this, sets all the subfields as the targets of the write operation. That is, when the reduction target SF number Nsf is “0”, the second image conversion unit 42 does not change the image data generated by the first image conversion unit 41 according to the predetermined coding shown in FIG. To each drive IC 521 of the data electrode drive circuit 52. When the normal image signal is supplied as described above, the plasma display device of the present embodiment performs display using all the set subfields by performing the above-described operation. Process.

  In particular, in the plasma display device according to the present embodiment, for example, the target SF number determination circuit 48 determines the target SF number Npe with two power threshold values in the power increasing direction and the decreasing direction, so that the time t1 in FIG. Even if the calculated power value may exceed one threshold as in the period up to, the number of target SFs Npe can be set to “0” and constant. That is, when only Pthd_min that does not depend on the power change direction is provided as the minimum power threshold, for example, the target SF number Npe varies between “0” and “1” with respect to the power calculation value PE as shown in FIG. 11A. Will be. On the other hand, in the plasma display device of the present embodiment, the target SF number determination circuit 47 has a temperature threshold value combining the temperature increasing direction and the decreasing direction as shown in FIG. In order to determine the number of target SFs based on the power threshold value combining the power increasing direction and the decreasing direction as shown in 10B, the fluctuation of the reduction target SF number Nsf is suppressed together with the target SF number Nte and the target SF number Npe. Can do. Further, it is possible to suppress flicker on the display image due to an operation in which gradation restriction and non-restriction are repeated.

  Next, in the period from time t1 to time t4 shown in FIGS. 11A, 11B, 11C, and 11D, a checkered image signal is input so that the relationship between the light emission states between the adjacent discharge cells is reversed. When such an image signal is input, as described above, the number of changes in the write pulse voltage increases, and thereby the power consumption of each drive IC 521 also increases. Since each load calculation circuit 601 detects the increased number of changes in this way, the load value output from each load calculation circuit 601 also increases rapidly. For this reason, as shown in FIG. 11A, the power calculation value PE output from the power calculation circuit 62 increases rapidly from time t1 to time t2, while exceeding the power maximum threshold Pthu_max in the target SF number determination circuit 48. It becomes. As a result, as shown in FIG. 11B, in the period from time t1 to time t2, the target SF number determination circuit 48 sequentially outputs “1”, “3”, and “8” as the value of the target SF number Npe.

  On the other hand, each cumulative calculator 611 of the temperature calculation circuit 61 cumulatively calculates the load value output from the load calculation circuit 601, and therefore, as shown in FIG. It increases slowly without increasing. For this reason, as shown in FIG. 11C, in the period from time t1 to time t2, the target SF number determination circuit 47 outputs “0” as the value of the target SF number Nte.

  The maximum value detector 433 detects the larger number of the target SF number Npe and the target SF number Nte. Therefore, as shown in FIG. 11D, in the period from time t1 to time t2, the maximum value detector 433 selects the number of target SFs Npe and sequentially reduces it to “1” “3” “8”. Conversion control data indicating the SF number Nsf is output. The second image conversion unit 42 receives the conversion control data in which the reduction target SF number Nsf is set to “1”, “3”, and “8” in order, and therefore the image data supplied from the first image conversion unit 41 is reduced. The number of subfields based on the number Nsf is changed to image data for which the writing operation is stopped. That is, when the reduction target SF number Nsf is “1”, the second image conversion unit 42 sets the first SF as a reduction target, and does not perform the first SF writing operation on the image data supplied from the first image conversion unit 41. Convert to image data changed to coding. Similarly, when the reduction target SF count Nsf is “3”, the first SF to the third SF are targeted for reduction, and the image data supplied from the first image conversion unit 41 is not subjected to the writing operation of the first SF to the third SF. Convert to image data changed to coding. When the number of SFs to be reduced Nsf is “8”, the second image conversion unit 42 sets the image data supplied from the first image conversion unit 41 to the first SF to the first SF with the first SF to the eighth SF as reduction targets. It is converted into image data that has been changed to coding that does not perform the 8SF writing operation. In this way, when an image signal whose power consumption increases abruptly is input, the second image conversion unit 42 responds to the power consumption that increases rapidly by feedback control via the power calculation circuit 62. Changes the image data supplied from the first image conversion unit 41 to image data that rapidly reduces power consumption.

  As described above, during the period from time t1 to time t2, the image data supplied from the first image conversion unit 41 is consumed by reducing the first SF to the eighth SF by feedback control via the power calculation circuit 62. Since the image data is changed so as to rapidly decrease the power, the power consumption of each drive IC 521 once increased rapidly decreases from around time t2. In other words, the feedback control operation via the power calculation circuit 62 continues from time t2 to time t3, and the power consumption of each drive IC 521 and the power calculation value PE gradually decrease accordingly. The number of SFs Npe also gradually decreases to “6” and “5” as shown in FIG. 11B.

  On the other hand, the temperature of each drive IC 521 gradually increases from around time t2 due to the increase in power consumption accompanying the change of the image signal after time t1. Along with this, the temperature calculation value TE gradually increases. For this reason, as shown in FIG. 11A, the temperature calculation value TE exceeds the temperature minimum threshold value Tthu_min in the target SF number determination circuit 47. As a result, as shown in FIG. 11C, the target SF number determination circuit 47 sequentially outputs “1”, “2”, and “3” as the value of the target SF number Nte from the middle of the period from time t2 to time t3. To do.

  When the target SF number Npe and the target SF number Nte are compared in the period from time t2 to time t3, as shown in FIGS. 11B and 11C, the target SF number Npe is still larger in this period. Therefore, the maximum value detector 433 selects the target SF number Npe which is the larger number even during the period from the time t2 to the time t3, and as illustrated in FIG. 11D, conversion control indicating the reduction target SF number Nsf. “6” and “5” are sequentially output as data. Further, the second image conversion unit 42 outputs the image data in which the writing of the target subfield is stopped according to the reduction target SF number Nsf. As described above, even after an image signal whose power consumption is rapidly increased is input, each drive IC 521 is controlled by feedback control via the power calculation circuit 62 during a period from time t2 to time t3. An operation is performed to gradually reduce the power consumption.

  Further, during the period from time t3 to time t4, the power consumption, the power calculation value PE, and the target SF number Npe of each drive IC 521 are stabilized to a substantially constant value by the feedback control as described above. On the other hand, the temperature of each drive IC 521 continues to gradually increase for a while after time t3 due to the increase in power consumption from time t1, and accordingly, the temperature calculation value TE and the target SF number Nte also gradually increase. To do. For this reason, as shown in FIGS. 11B and 11C, after time t3, the target SF number Nte is larger than the target SF number Npe, and the maximum value detector 433 selects the target SF number Nte. As illustrated in 11D, “5”, “6”, and “5” are sequentially output as conversion control data indicating the number of SFs Nsf to be reduced. Further, the second image conversion unit 42 converts the image data supplied from the first image conversion unit 41 into image data having a subfield that is not subjected to a writing operation according to the reduction target SF number Nsf, and outputs the image data. . In this way, after a certain time has elapsed after an image signal that increases power consumption is input, the control shifts to feedback control via the temperature calculation circuit 61, and the temperature rises together with the power consumption of each drive IC 521. An operation that suppresses this is executed. Note that, like the conversion control data generation unit 46, the maximum value detector 433 is configured to obtain the larger value of the target SF number Npe based on power consumption and the target SF number Nte based on temperature. Accordingly, the power consumption of each drive IC 521 can be suppressed based on at least one of the power consumption and the temperature, and the feedback control for each of the power consumption and the temperature can be switched with a simple configuration.

  As described above, when an image signal that increases the power consumption of the data electrode driving circuit 52 is input during the period from the time t1 to the time t4, the plasma display device according to the present embodiment first calculates the power. By feedback control that suppresses the power consumption via the circuit 62, it responds immediately to the increase in power consumption and operates to rapidly decrease the power consumption. Then, the plasma display device responds to the gradually increasing temperature by feedback control that suppresses the temperature increase via the temperature calculation circuit 61 so as to suppress the temperature increase along with the power consumption. Operate. For this reason, when an image signal that increases power consumption is input, for example, compared with a method of lowering the temperature of the data electrode drive circuit by temperature feedback control, the plasma display device of the present embodiment is The power consumption is immediately suppressed, thereby suppressing the temperature rise.

  Further, when switching to a normal image at time t4, the number of changes in the write pulse voltage decreases, so the load value output from each load calculation circuit 601 also decreases. Along with this, the power calculation value PE and the target SF number Npe also decrease, and the temperature calculation value TE and the target SF number Nte also decrease slowly. Thereafter, when the number of SFs Nsf to be reduced in the conversion control data is reduced to “0”, the image signal conversion circuit 400 converts the image data according to the predetermined coding shown in FIG. 52 is supplied to each of the driving ICs 521, and the panel 10 displays an image in accordance with a predetermined coding that does not stop the subfield writing.

  In the case of the above-described configuration, for example, when the temperature calculation value TE repeatedly rises and falls between the temperature threshold value Tthu and the temperature threshold value Tthd, which are one combination, the target SF number Nte is set with the threshold value combined therewith. In order to determine, the target SF number Nte also vibrates with this repetition. FIG. 12A is a diagram illustrating a state in which the value of the target SF number Nte vibrates when the temperature calculated value TE repeatedly rises and falls between the two threshold values. FIG. 12A shows an example in which the temperature calculation value TE repeatedly rises and falls between the temperature maximum threshold value Tthu_max and the temperature maximum threshold value Tthd_max. That is, in the direction in which the calculated temperature value TE rises, when the calculated temperature value TE is equal to or lower than the maximum temperature threshold value Tthu_max as shown by time t11 in FIG. 12A, the target SF number Nte is “7”. When the calculated temperature value TE exceeds the maximum temperature threshold value Tthu_max, “8” is set. On the other hand, if the calculated temperature value TE exceeds the maximum temperature threshold value Tthd_max, such as from time t11 to time t12, in the direction in which the calculated temperature value TE decreases, the target SF number Nte becomes “8”.

  Then, when the temperature is equal to or lower than the temperature maximum threshold value Tthd_max after time t14, the value becomes “7”. Therefore, as in the period from time t10 to time t14, when the calculated temperature value TE exceeds the maximum temperature threshold value Tthd_max and is equal to or lower than the maximum temperature threshold value Tthu_max, depending on whether the calculated temperature value TE increases or decreases, As shown in 12A, the number of target SFs Nte fluctuates between “7” and “8”, and such fluctuation causes flicker on the display screen, resulting in a reduction in image quality.

  FIG. 12B is a diagram illustrating an example of an operation by the process for suppressing the vibration of the target SF number Nte when the calculated temperature value TE repeatedly increases and decreases between the temperature threshold value Tthu and the temperature threshold value Tthd. It is. As this processing, as shown in FIG. 12B, at time t10, first, it is detected that the calculated temperature value TE has exceeded the temperature threshold value Tthd_max as the temperature has increased, and has reached a value between the temperature threshold value Tthu_max and the temperature threshold value Tthd_max. To do. After this detection, whether the temperature calculation value TE is reversed from rising to falling in a period (period from time t10 to time t14) in which the temperature calculation value TE is a value between the temperature threshold value Tthu_max and the temperature threshold value Tthd_max The detection of whether or not the temperature calculation value TE is equal to or lower than the temperature threshold value Tthd_max is also started. That is, as shown in FIG. 12B, it is detected that the temperature calculated value TE is reversed from rising to falling (indicated by reference numeral 120). When the calculated temperature value TE is not equal to or lower than the temperature threshold value Tthd_max (time t11), the use of the current temperature threshold value Tthu_max is started as the temperature threshold value for determining the target SF number Nte (indicated by reference numeral 122). . Further, thereafter, until the temperature calculation value TE becomes equal to or lower than the temperature threshold value Tthd_max, the use of the temperature threshold value Tthu_max as the temperature threshold value for determining the target SF number Nte is continued, and the temperature calculation value TE becomes equal to or lower than the temperature threshold value Tthd_max. At the time (time t14), the use of the temperature threshold value Tthu_max is released (indicated by reference numeral 124). That is, the period from time t11 to time t14 is shown as a period 126 during which the use of the temperature threshold value Tthu_max is continued. By executing such processing, as illustrated in FIG. 12B, the target SF number Nte becomes a constant “7”, and the target SF number Nte fluctuates between “7” and “8”. Can be suppressed.

  FIG. 12B illustrates an example in which the temperature calculation value TE increases and the temperature calculation value TE becomes a value between the temperature maximum threshold value Tthu_max and the temperature maximum threshold value Tthd_max. The present invention is also applicable to a case where the value is between the combined temperature threshold value Tthu and the temperature threshold value Tthd. In addition, when the temperature calculation value TE decreases, by performing a process opposite to the above process, it is possible to similarly suppress the variation in the target SF number Nte. That is, first, it is detected that the temperature calculation value TE is equal to or lower than the temperature threshold value Tthu and is between the temperature threshold value Tthu and the temperature threshold value Tthd. After this detection, in a period in which the temperature calculation value TE is a value between the temperature threshold value Tthu and the temperature threshold value Tthd, detection of whether or not the temperature calculation value TE is reversed from a decrease to an increase starts, and the temperature calculation Detection of whether the value TE is equal to or higher than the temperature threshold Tthu is also started. When the temperature calculation value TE is reversed from a decrease to an increase and the temperature calculation value TE is not equal to or higher than the temperature threshold value Tthu, the current temperature threshold value Tthd is used as the temperature threshold value for determining the target SF number Nte. . Further, thereafter, the temperature threshold value Tthd is continuously used as the temperature threshold value for determining the target SF number Nte until the temperature calculated value TE becomes equal to or higher than the temperature threshold value Tthu, and the temperature calculated value TE becomes equal to or higher than the temperature threshold value Tthu. At that time, the use of the temperature threshold value Tthd is released. By executing such processing, it can be applied to the case where the temperature calculated value TE is lowered, contrary to FIG. 12B. In the above description, the temperature calculation value TE has been described as an example. However, by performing the same process on the power calculation value PE, the number of target SFs Npe due to the power calculation value PE can be changed. Further suppression can be achieved.

  As described above, the plasma display device according to the present embodiment includes the power calculation circuit 62 that calculates the power consumption of the data electrode drive circuit 52 based on the image data, and the temperature of the data electrode drive circuit 52 based on the image data. And a temperature change detection circuit 63 for detecting a temperature change direction of whether the calculated temperature rises or falls per unit time, and the calculated power rises per unit time. And a power change detection circuit 64 for detecting a power change direction of whether to move or to descend. The image signal conversion circuit 400 outputs the image signal to the data electrode driving circuit 52 when at least the calculated power consumption exceeds the first power threshold value or when the calculated temperature exceeds the first temperature threshold value. Convert to image data to reduce power consumption. In addition, the image signal conversion circuit 400 outputs the image signal to the data electrode drive circuit when at least the calculated power consumption is equal to or lower than the second power threshold or when the calculated temperature is equal to or lower than the second temperature threshold. The image data is converted into image data that increases power consumption. Note that, as described above, a configuration may be adopted in which one of power consumption and temperature is determined based on whether it is greater than a predetermined threshold regardless of the direction of change. With such a configuration, the plasma display apparatus according to the present embodiment first performs feedback control via the power calculation circuit 62 that suppresses power consumption, such as when an image signal that increases power consumption is input. Thus, the power consumption is rapidly reduced, and then the temperature rise is suppressed together with the power consumption by feedback control that suppresses the temperature rise via the temperature calculation circuit 61. Furthermore, in the plasma display device according to the present embodiment, the image signal conversion circuit 400 converts the image data into image data that reduces power consumption based on a predetermined power threshold corresponding to the power change direction and a predetermined temperature threshold corresponding to the temperature change direction. Therefore, the fluctuation of the conversion control data for controlling the conversion to the image data that reduces the power consumption can be suppressed, and the display image can be displayed on the display image by repeating the gradation limitation and non-limitation. Flicker can also be suppressed, and deterioration in image quality can be suppressed.

  Therefore, according to the plasma display device of the present invention, it is possible to respond immediately to a rapid increase in power consumption, and to perform image display with stable operation without malfunction of the data electrode driving circuit. A plasma display device can be provided.

  In the above description, in order to make the description easy to understand, a configuration example in which the target SF number Npe based on the load value calculated by each load calculation circuit 601 is fed back without delay has been described. In order to suppress response characteristics, elements such as a simple loop filter having a small time constant may be added as appropriate. Further, in order to realize the rapid rise characteristic of the target SF number Npe in the period from time t1 to time t2 as shown in FIG. 7B and FIG. 11B, for example, the maximum number of target SF numbers Npe and the number of changes per field are set in advance. In addition to setting, one threshold value for the power calculation value PE is provided, and when the power calculation value PE exceeds this threshold value, the number of target SFs Npe that changes to the maximum number for each field is changed to the second image conversion. A configuration for supplying to the unit 42 is also possible.

  Further, in the first and second embodiments, a configuration example in which the temperature calculation value TE and the power calculation value PE based on the load value calculated by each load calculation circuit 601 are fed back and the coding is changed to reduce power consumption. As described above, the present invention is not limited to this configuration. For example, the temperature calculation value TE is fed back and the power calculation value PE is fed forward to change the coding to reduce power consumption. It may be a configuration.

  In addition, the specific numerical values used in the first and second embodiments are merely examples, and may be appropriately set to optimum values according to panel characteristics, plasma display device specifications, and the like. desirable.

  The plasma display device of the present invention can immediately respond to a rapid increase in power consumption and the like, and can display an image with a stable operation without malfunction of the data electrode driving circuit. It is useful as a display device used for large monitors.

The disassembled perspective view which shows the principal part of the panel in embodiment of this invention Electrode arrangement of the panel The figure which shows the drive voltage waveform impressed to each electrode of the panel Circuit block diagram of plasma display device according to Embodiment 1 of the present invention The figure which shows an example of the relationship between the image signal and image data in embodiment of this invention The figure which is another example of the relationship between the image signal and image data in embodiment of this invention, Comprising: The figure which shows the coding which does not perform writing operation by 1st SF The figure which is another example of the relationship between the image signal and image data in embodiment of this invention, Comprising: The figure which shows the coding which does not perform writing operation by 1st SF and 2nd SF FIG. 3 is a circuit block diagram showing a detailed configuration example of a main part of the circuit configuration for controlling the power consumption of the plasma display device in the first exemplary embodiment of the present invention. The figure which showed the operation example which produces | generates the conversion control data of the plasma display apparatus in Embodiment 1 of this invention The figure which showed the operation example which produces | generates the conversion control data of the plasma display apparatus in Embodiment 1 of this invention, and showed the number of object SFs which the object SF number determination circuit determined based on the power calculation value The figure which showed the operation example which produces | generates the conversion control data of the plasma display apparatus in Embodiment 1 of this invention, and showed the number of object SFs which the object SF number determination circuit determined based on the temperature calculation value The figure which showed the operation example which produces | generates the conversion control data of the plasma display apparatus in Embodiment 1 of this invention, and showed the reduction target SF number which is the larger number which the maximum value detector detected among object SF numbers Circuit block diagram of plasma display device in accordance with the second exemplary embodiment of the present invention The circuit block diagram which shows the detailed structural example of the circuit structure principal part for controlling the power consumption of the plasma display apparatus in Embodiment 2 of this invention The figure which shows an example of the temperature threshold value Tthu and temperature threshold value Tthd which were set in order to determine the object SF number Nte in Embodiment 2 of this invention The figure which shows an example of the power threshold value Pthu and power threshold value Pthd which were set in order to determine the object SF number Npe in Embodiment 2 of this invention The figure which showed the operation example which produces | generates the conversion control data of the plasma display apparatus in Embodiment 2 of this invention. The figure which showed the operation example which produces | generates the conversion control data of the plasma display apparatus in Embodiment 2 of this invention, and showed the number of object SFs which the object SF number determination circuit determined based on the power calculation value The figure which showed the operation example which produces | generates the conversion control data of the plasma display apparatus in Embodiment 2 of this invention, and showed the number of object SFs which the object SF number determination circuit determined based on the temperature calculation value The figure which shows the operation example which produces | generates the conversion control data of the plasma display apparatus in Embodiment 2 of this invention, and showed the reduction target SF number which is the larger number which the maximum value detector detected among object SF numbers The figure which shows a mode that the value of object SF number Nte vibrates when the temperature calculation value TE repeats a raise and fall between the temperature threshold value Tthu and the temperature threshold value Tthd in Embodiment 2 of this invention. The figure which showed one operation example by the process for suppressing the vibration of object SF number Nte in the same case

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Panel 21 Front substrate 22 Scan electrode 23 Sustain electrode 24 Display electrode pair 25,33 Dielectric layer 26 Protective layer 31 Back substrate 32 Data electrode 34 Partition 35 Phosphor layer 40,400 Image signal conversion circuit 41 1st image conversion part 42 Second image conversion unit 43, 46 Conversion control data generation unit 44, 45, 47, 48 Target SF number determination circuit 52 Data electrode drive circuit 53 Scan electrode drive circuit 54 Sustain electrode drive circuit 55 Timing generation circuit 60 Data electrode load calculation circuit 61 Temperature calculation circuit (temperature calculation unit)
62 Power Calculation Circuit (Power Calculation Unit)
63 Temperature change detection circuit 64 Power change detection circuit 433, 612 Maximum value detector 521 Drive IC (drive unit)
601 Load calculation circuit 611 Cumulative computing unit 621 Adder

Claims (5)

A plasma display panel in which discharge cells are formed at intersections between display electrode pairs and data electrodes is used, and one field period of an image signal is divided into a plurality of subfields, and the discharge cells emit light in each of the subfields. A plasma display device that displays an image by non-light emission,
An image signal conversion circuit for converting the image signal into image data for causing the discharge cells to emit or not emit light in each of the subfield periods;
A data electrode driving circuit for driving the data electrode based on the image data;
A power calculation unit that calculates power consumption of the data electrode driving circuit based on the image data and outputs the calculated power value ;
A temperature calculator that calculates the temperature of the data electrode drive circuit based on the image data and outputs the calculated temperature as a temperature calculated value ;
The image signal conversion circuit determines the number of subfields to be converted into image data that reduces power consumption of the data electrode driving circuit according to each of the power calculation value and the temperature calculation value, and sets the number of target SFs. Converting the image signal into the image data based on a larger one of the number of target SFs determined according to the calculated power value and the number of target SFs determined according to the temperature calculated value. A characteristic plasma display device. The image signal conversion circuit has a first temperature threshold value and a second temperature threshold value smaller than the first temperature threshold value,
The image signal conversion circuit, when at least the calculated power value exceeds a predetermined power threshold value, or when the calculated temperature value exceeds the first temperature threshold value , converts the image signal to the data electrode driving circuit. Convert to the image data to reduce power consumption,
The image signal conversion circuit outputs the image signal to the data electrode when at least the calculated power value is equal to or less than the predetermined power threshold value, or when the calculated temperature value is equal to or less than the second temperature threshold value. The plasma display device according to claim 1, wherein the plasma display device converts the image data into image data that increases power consumption of the drive circuit. The image signal conversion circuit has a first power threshold value and a second power threshold value smaller than the first power threshold value,
The image signal conversion circuit outputs the image signal to the data electrode driving circuit when at least the power calculation value exceeds the first power threshold value or when the temperature calculation value exceeds a predetermined temperature threshold value. Convert to image data to reduce power consumption,
The image signal conversion circuit outputs the image signal as the data electrode when at least the calculated power value is equal to or lower than the second power threshold value or when the calculated temperature value is equal to or lower than the predetermined temperature threshold value. The plasma display device according to claim 1, wherein the plasma display device converts the image data into image data that increases power consumption of the drive circuit. The data electrode driving circuit has a plurality of driving units respectively corresponding to the data electrodes of the plasma display panel divided into blocks.
The power calculation unit calculates total power consumption of the plurality of drive units,
The plasma display apparatus of claim 1, wherein the temperature calculation unit calculates the highest temperature among the plurality of driving units. The plasma display apparatus according to claim 1, wherein the image signal conversion circuit reduces power consumption of the data electrode driving circuit in at least one of the subfields.

Images